Loose ligaments

I've been doing yoga twice a week for two weeks now and my right patellar tendon has started to hurt. That puzzled me because that's my "good knee". I talked with the instructor today and she reminded me that a pregnant woman's ligaments loosen quite a bit in preparation for the birth. So my "bad knee" is probably just getting close to "normal" because of all of the scar tissue, and the "good knee" is loosening up a lot. I am skipping some of the poses and modifying some, but overall I like the class. Yoga is a lot harder work than it appears to be.